1. Field of the Invention
The present invention relates to a phase locked loop and more particularly to a phase locked loop which is suitable for the case where the ratio between the input signal and output signal is not a simple integer.
2. Description of the Prior Art
A phase locked loop (PLL) is generally formed of a phase comparator 1, low-pass filter 2, voltage-controlled oscillator 3, and a frequency dividing circuit 4 as shown in FIG. 10, and the output f.sub.o is synchronized with the input frequency f.sub.r in the relationship EQU f.sub.o =Nf.sub.r,
where N is the dividing ratio of the frequency dividing circuit 4.
However, is a TBC (Time Base error Corrector) for removing the jitter along time axis of a regenerated video signal, a phase locked loop in which the ratio between the input frequency and output frequency is not a simple integer is required for restoration of the interleave of the luminance signal and color signal.
The foregoing results from the fact that the color subcarrier frequency f.sub.sc in the PAL system is set up such that: EQU f.sub.sc =(1135/4)f.sub.H+ (1/2) f.sub.V,
where
f.sub.H =horizontal scanning frequency and PA1 f.sub.V =vertical scanning frequency.
Since the offset frequency (1/2)f.sub.V is added as above, in the case where the color subcarrier frequency f.sub.sc is formed with the horizontal scanning frequency f.sub.H taken as the reference signal, the color subcarrier frequency for the PAL system cannot be formed by the phase locked loop shown in FIG. 10.